Machine-to-machine (M2M) communication enables machines to exchange short command and control messages. The main design goal is to achieve fast and highly reliable transmission of short messages over wireless channels with relatively simple devices having a small number of antennas, preferably one or two. One of the major application of M2M is in factories wherein automated production processes benefit when machines can communicate directly with each other wirelessly.
A single-input single-output (SISO) communication system with block transmission and detection is a candidate for M2M. The type of messages should use small block sizes, e.g., less than 100 symbols.
One M2M communication system uses pseudo-random phase precoding (PRPP) and likelihood ascent search (LAS) detection. That scheme performs extremely well in practice when the block size is at least 400 symbols. However, the goal is to greatly reduce the block size without degrading performance.
Maximum likelihood detection (MLD) is an optimal symbol detection scheme. However, the complexity of MLD increases exponentially with the block size. Therefore, a variety of suboptimal detection methods with polynomial complexity have been developed. One of the best known is probabilistic data association (PDA).
PDA was originally developed for radar target tracking and has gained interest in wireless communication applications. As such, PDA has been applied for multiuser detection in code division multiple access (CDMA) systems, turbo equalization, multiple input multiple output (MIMO) systems, and decision feedback equalization (DFE) for detecting symbols transmitted in MIMO systems over a frequency selective channel. A bit-by-bit detection of a higher order quadrature amplitude modulation (QAM) using the PDA method is also known.